Wireless communication networks are very popular these days. The popularity of wireless LANs is a testament primarily to their convenience, cost efficiency, and ease of integration with other communication networks and network components. In a wireless communication network, various communication devices interact with each other without any electronic conductors or wires. These days wireless communication devices are important tools for transmitting and receiving data and information over a wireless communication link or a wireless transmission channel. Examples of the wireless communication network include a Wireless Local Area Network (WLAN), a Wireless Wide Area Network (WWAN), a Wireless Fidelity Network (Wi-Fi), a Wireless Interoperability for Microwave Access (WIMAX), a High Performance Radio Local Area Network (HIPERLAN), etc. Examples of the wireless communication link or a wireless transmission channel include, but are not limited to, a radio wave link, an electromagnetic wave link, a Bluetooth® link, a microwave link, and an Infrared Data Association (IrDA) link.
Each node in the wireless communication network has a specified communication range. A node can directly transmit the data frames to only those nodes that are within the specified communication range of the node. In the wireless communication network a single wireless transmission channel is shared by more than one node that is in same communication range. These nodes transfer data frames from one node to another by using the wireless transmission channel. The communication range of a node depends on the transmit power level that is being used by the node to transmit the data frame. If the transmit power level used by the node is high then the communication range of the node will cover more number of nodes. However, if the transmit power level used by the node is low, then the communication range of the node will cover less number of nodes. The high transmit power level results in more interference among nodes that are in the same communication range and therefore reduces the capacity of the wireless communication network. The nodes that are out of communication range of a node are hidden to the node; and hence, the node cannot sense the presence or any transmission activity on these nodes. Such nodes are called hidden nodes or hidden terminals. Increment in the number of hidden nodes leads to more collisions in the wireless transmission channel and results in unsuccessful transmissions and loss of data or information in the wireless communication network. When two or more nodes simultaneously transmit data frames to a destination node, then a data frame transmitted using higher transmit power level might be successfully delivered at the destination node. Simultaneously, the data frames transmitted using lower transmit power level are suppressed at the destination node. This phenomenon is known as capture effect. According to the principles of capture effect, the data frame that was transmitted using a lower transmit power level is suppressed by the data frame transmitted using the higher transmit power level, and only the data frame transmitted using higher transmit power level might receive successfully at the destination node if the differentiation between the higher and lower transmit power level is big enough.
There are several methods that exist to solve the hidden terminal problem and to manage transmission of data frames in the wireless communication network. One of these methods uses a close loop (e.g. Ready to Send (RTS)/Clear to Send (CTS) frames) or open loop communication between a sending node and a receiving node. The open or close loop communication facilitates exchange of information, such as reception characteristics of the receiving node, to sense the wireless transmission channel prior to the actual data transmission. This practice ensures use of optimal transmit power for the actual data transmission at the sending node. In this method, a sending node sends an RTS frame to the receiving node, and the actual data frame is sent only when the sending device has received a CTS frame from the receiving node. The exchange of RTS/CTS only partially reduces the impact of the hidden terminal problem. The exchange of RTS/CTS frame itself can suffer from the hidden terminal problem, in particular when the sender employs very aggressive contention parameters.
Moreover, the transmit power level, once increased, is not decreased after resolving the hidden terminal problem and all the subsequent transmissions take place at the increased transmit power level. The increased transmit power level results in more interference among nodes, and therefore are very likely to reduce the capacity of the wireless communication network. Hence, such a method increases interference of nodes in the transmission channel and also consumes a lot of power while transmitting the data frame.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated, relative to other elements, to help in improving an understanding of the embodiments of the present invention.